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Abstract:

A chassis dynamometer for a vehicle has a motor having a rotor, rollers on
which wheels of the vehicle are disposed, a flange portion extending
inward in a radial direction from each of the rollers, and a rotor
bracket for supporting the rotor of the motor. The flange portion and the
rotor bracket are connected via a torque meter capable of measuring at
least an outer peripheral tangential force of said roller.

Claims:

1. A chassis dynamometer for a vehicle comprising:a motor; androllers
configured to be operably connected to wheels of the vehicle,wherein at
least part of the motor is disposed inward in a radial direction of each
of the rollers.

2. A chassis dynamometer according to claim 1, wherein said motor includes
a stator fitted to a base seat and a rotor fitted to said roller so as to
rotate integrally with said roller.

3. A chassis dynamometer according to claim 2, wherein said stator is
disposed outward in the radial direction with respect to said rotor.

4. A chassis dynamometer according to claim 2, wherein said stator is
disposed inward in the radial direction with respect to said rotor.

5. A chassis dynamometer for a vehicle comprising:a motor comprising a
rotor;rollers configured to be operably connected to wheels of the
vehicle;a flange portion extending inward in a radial direction from each
of the rollers; anda rotor bracket for supporting the rotor of the
motor,wherein the flange portion and the rotor bracket are connected via
a torque meter capable of measuring at least an outer peripheral
tangential force of said roller.

6. A chassis dynamometer according to claim 5, wherein said motor is
disposed inward in the radial direction of said roller.

7. A chassis dynamometer according to claim 5, wherein said torque meter
is a six-force-component meter.

8. A chassis dynamometer according to claim 1, wherein said rollers and
said motors are provided on a plurality-by-plurality basis and operate
independently.

9. A chassis dynamometer according to claim 6, wherein said torque meter
is a six-force-component meter.

10. A chassis dynamometer according to claim 2, wherein said rollers and
said motors are provided on a plurality-by-plurality basis and operate
independently.

11. A chassis dynamometer according to claim 3, wherein said rollers and
said motors are provided on a plurality-by-plurality basis and operate
independently.

12. A chassis dynamometer according to claim 4, wherein said rollers and
said motors are provided on a plurality-by-plurality basis and operate
independently.

13. A chassis dynamometer according to claim 5, wherein said rollers and
said motors are provided on a plurality-by-plurality basis and operate
independently.

14. A chassis dynamometer according to claim 6, wherein said rollers and
said motors are provided on a plurality-by-plurality basis and operate
independently.

15. A chassis dynamometer according to claim 7, wherein said rollers and
said motors are provided on a plurality-by-plurality basis and operate
independently.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a chassis dynamometer for detecting
torque of drive wheels of a vehicle.

[0002]The chassis dynamometer is generally employed for conducting a
dynamic traveling performance test of the vehicle indoors. More
specifically, the chassis dynamometer is constructed so that the drive
wheels of the vehicle are placed on rotatable rollers in place of a road
surface and set in a traveling state, the torque is measured by
transferring the torque of the drive wheels to the rollers, and
predetermined resistance (traveling resistance) received by the wheels
from the road surface can be given in the dynamic test such as a variety
of acceleration tests and exhaust gas mode tests.

[0003]The chassis dynamometer in the prior art is exemplified in FIG. 1.
In FIG. 1, a motor M is installed on a base B placed on a ground surface
or a floor surface. Two rollers R1, R2 are connected to a rotary shaft S
protruding from one side of the motor M, and an end portion of the rotary
shaft S is rotatably supported by a pillar-post P.

[0004]Another type of chassis dynamometer in the prior art is exemplified
in Patent document 1, and FIG. 2 shows a schematic view thereof. In FIG.
2, the motor M is placed on the base B installed on the ground surface or
the floor surface. The two rollers R1, R2 are connected to the cantilever
type rotary shaft S protruding from both sides of the motor M.

[0005]According to this type of chassis dynamometer, drive wheels T, T of
a vehicle V are placed on the rollers R1, R2, and the rollers R1, R2 are
rotated by driving force thereof, thereby enabling a torque meter to
measure the torque. Further, the motor M rotates the rotary shaft S to
transfer power to the drive wheels T, T via the rollers R1, R2, thereby
enabling the resistance of the driving system of the vehicle to be
measured.

[0006]By the way, as illustrated in FIGS. 1 and 2, in the case of
disposing the rollers R1, R2 on the rotary shaft S of the motor M, a
shaft-end load applied to the rotary shaft S of the motor M increases,
which entails taking it into consideration to raise a flexural strength
and a withstand load of a bearing in terms of a structural design. By
contrast, it can be also considered to enlarge a diameter of the rotary
shaft S and to increase a load capacity of the bearing, however, the
apparatus is to be upsized in order to increase the structural strength,
and a cost might be raised. Another thinkable scheme is a structure for
supporting the both sides of the rollers R1, R2 with the bearings,
however, the increase in the number of the bearings leads to a large loss
of the mechanical rotations, resulting in a possibility of deterioration
of measuring accuracy.

[0007]Moreover, as far as the rollers R1, R2 each having a large inertial
mass are connected to the rotary shaft S, such a state arises that the
torsion rigidity of a rotation system decreases and a torsion resonance
frequency decreases. If intended only to increase the torsion rigidity,
it may be sufficient that the rotary shaft be thickened, however, the
thickened shaft leads to an ill-balanced structure and an upsizing
problem which will arise. Additionally, when a shaft torque meter is
inserted on the side of the rotary shaft, the rigidity of the rotary
shaft further decreases, and fluctuations in torque might be caused with
rotations at a torsion resonance point.

[0008]Furthermore, in the chassis dynamometers in FIGS. 1 and 2, the
rollers R1, R2 are fixed to the rotary shaft, and hence it is required
that widths of the rollers R1, R2 be previously ensured large enough to
have flexibility to vehicles each having a different width. When
increasing the widths of the rollers R1, R2, however, there arises a
problem that the inertial mass further increases. Particularly, there is
a request for performing a test for a low μ path on the chassis
dynamometer, which entails reducing the inertial masses of the rollers
R1, R2 to the greatest possible degree, and, though the roller width is
desired to be as narrow as possible, such a problem occurs that the
test-enabled vehicles are restricted if the widths of the rollers R1, R2
are narrowed. Especially in the chassis dynamometer in FIG. 2, the motor
M is located between the rollers R1, R2, and this arrangement becomes a
restriction on the occasion of narrowing an interval between the rollers
R1, R2 and might disable a vehicle with a narrow tread such as a light
car from undergoing a test.

[0009]On the other hand, a technique of enabling a frame of the motor to
oscillate, then measuring a force receiving as reaction by a load cell
via an arm and converting the force into torque, is known as one
technique of measuring the torque in the conventional chassis
dynamometer. Further, another known technique of measuring the torque is
a technique of fitting a shaft torque meter to an output shaft of the
motor and directly measuring the torque. In order to obtain more of
accuracy for the measurement, however, a loss of the bearing and a
windage loss are measured beforehand, and it is necessary to take a
technique for canceling these losses.

[0010]Since the loss of the bearing greatly changes depending on a weight
of the vehicle and a temperature during an operation, it is difficult to
specify the loss with high accuracy, and it is therefore extremely hard
to make the precise measurement. Moreover, the oscillation-based
measuring technique has a problem in terms of low rigidity caused from a
frame of the motor and a spring constant of the load cell, and has a
tendency of being unable to evaluate quickly due to a delay of response
of the measurement. By contrast, the measurement, which involves using
the shaft torque meter, takes a structure decreasing the rigidity of the
rotation system in many cases, then it follows that there exists
resonance in the mechanical system having a low frequency, and a problem
is that a demanded design is the design causing no overlap of the
rotating speed in a measuring range. Note that Patent document 2
discloses a configuration for measuring the torque of the wheel of the
vehicle and correcting the absorption torque of the motor, but has a
problem that the configuration gets complicated. [0011][Patent document
1] Japanese Patent Laid-Open Publication No. H06-50850 [0012][Patent
document 2] Japanese Patent Laid-Open Publication No. H05-240739

DISCLOSURE OF THE INVENTION

[0013]It is an object of the present invention, which was devised in view
of the problems inherent in the prior arts, to provide a compact chassis
dynamometer capable of performing a high-accuracy test or a high-accuracy
measurement about a variety of vehicles.

[0014]A chassis dynamometer according to a first invention is
characterized in that at least part of a motor is disposed inward in a
radial direction of each of rollers on which to place wheels of a
vehicle.

[0015]A chassis dynamometer according to a second invention is
characterized in that a flange portion extending inward in a radial
direction from each of rollers on which to place wheels of a vehicle and
a rotor bracket for supporting a rotor of a motor are connected via a
torque meter capable of measuring at least an outer peripheral tangential
force of the roller.

[0016]According to the chassis dynamometer in the first invention, at
least part of the motor is disposed inward in the radial direction of
each of the rollers on which to place the wheels of the vehicle, whereby
a rotary shaft of the motor can be shortened or eliminated as the case
may be, then torsion rigidity of a rotation system is increased though
schemed to thereby save a space, and a rotational balance can be improved
by concentrating heavy masses. Moreover, since a vehicle load can be
applied from outward in the radial direction to bearings that bear the
rollers, a flexural moment does not act unlike a case of supporting a
rotary shaft as by a conventional technology, and a long life-span of the
bearing can be ensured. Moreover, the motor is provided inwardly of the
rollers, and hence a distance between the rollers can be arbitrarily set.
Accordingly, the same chassis dynamometers are installed in adjustment to
positions of the individual wheels of the vehicle, whereby a width of the
roller can be reduced, an inertial mass can be restrained small, and
consequently a test for a low μ path can be reenacted on a bench.

[0017]It is preferable that the motor includes a stator fitted to a base
seat and a rotor fitted to the roller so as to rotate integrally with the
roller.

[0018]When the stator is disposed outward in the radial direction with
respect to the rotor, the motor serving as an in-roller motor generating
the high torque can be incorporated into the roller.

[0019]When the stator is disposed inward in the radial direction with
respect to the rotor, the motor serving as the in-roller motor generating
the high torque can be incorporated into the roller.

[0020]According to the chassis dynamometer in the second invention, the
flange portion extending inward in the radial direction from each of the
rollers on which to place the wheels of the vehicle and the rotor bracket
for supporting the rotor of the motor are connected via the torque meter
capable of measuring at least the outer peripheral tangential force of
the roller, thereby enabling the measurement of the torque to be avoided
from being affected by the bearing. Accordingly, an error in the
measurement of the torque is caused mainly by a windage loss of the
roller. The windage loss, which is determined based on the structure of
the roller and can be reduced to the greatest possible degree, takes a
stable value without being influenced by a temperature after the
structure has been determined and can be precisely corrected. Namely,
according to the present invention, the precise measurement, which was
not attained by the prior arts, can be realized. Further, there is no
necessity for providing the rotary shaft of the motor with the shaft
torque meter, and therefore the torsion rigidity can be designed to be
extremely high in terms of a mechanical structure, whereby an evaluation
of the measurement of the torque in a fast response can be actualized.

[0021]When the motor is disposed inward in the radial direction of the
roller, the rotary shaft of the motor can be shortened or eliminated as
the case may be, then the torsion rigidity of the rotation system is
increased though schemed to thereby save the space, and the rotational
balance can be improved by concentrating the heavy masses.

[0022]It is preferable that the torque meter is a six-force-component
meter because of being capable of measuring an outer peripheral
tangential force acting on the roller, i.e., the force components other
than in the traveling direction of the vehicle.

[0023]When the rollers and the motors are provided on a
plurality-by-plurality basis and operate independently, the chassis
dynamometers are provided for the respective drive wheels of an
all-wheel-drive vehicle, whereby each drive wheel can be tested.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 A schematic view showing a chassis dynamometer in a
conventional example.

[0025]FIG. 2 A perspective view showing the chassis dynamometer in the
conventional example.

[0026]FIG. 3 A perspective view showing a state where the chassis
dynamometer according to the present embodiment is installed on a bench.

[0027]FIG. 4 A sectional view, taken in a direction of the axial line, of
a chassis dynamometer 100 according to the present embodiment.

[0028]FIG. 5 A view of a configuration in FIG. 4 as viewed in an arrowhead
direction V.

[0029]FIG. 6 An enlarged view of a portion depicted along an arrowhead VI
in the configuration in FIG. 4.

[0031]FIG. 8 A view of the configuration cut off by a VIII-VIII line and
viewed in the arrowhead direction in FIG. 7.

[0032]FIG. 9 A view showing a force acting on between a roller 109 and a
wheel T when measured.

[0033]FIG. 10 A sectional view taken in the direction of the axial line,
showing a chassis dynamometer 100' according to another embodiment.

[0034]FIG. 11 A view of the configuration in FIG. 10 as viewed in an
arrowhead direction XI.

[0035]FIG. 12 An enlarged view of a portion depicted along an arrowhead
line XII in the configuration in FIG. 10.

BEST MODE FOR CARRYING OUT THE INVENTION

[0036]An embodiment of the present invention will hereinafter be described
with reference to the drawings. FIG. 3 is a perspective view showing a
chassis dynamometer in a state of being installed on a bench according to
the present embodiment. Referring to FIG. 3, two pieces of the same
chassis dynamometers 100 are disposed in a way that has a common axial
line of rotations. Drive wheels T, T of a vehicle V are placed on rollers
of the chassis dynamometers 100.

[0037]FIG. 4 is a sectional view taken in a direction of the axial line of
the chassis dynamometers 100 according to the present embodiment. FIG. 5
is a view of the configuration as viewed in an arrowhead direction V. In
FIG. 4, an L-shaped base seat 101 is fixed to a floor surface with bolts,
and eyebolts 101a for suspension are screwed to an upper portion thereof.

[0038]FIG. 6 is an enlarged view showing a portion depicted along an
arrowhead VI in the configuration in FIG. 4. Referring to FIG. 6, a
disc-shaped base 102 is fixed to an upper side face of the base seat 101
with bolts. A fixed shaft 103 is fixed to the base 102 with the bolts.
The fixed shaft 103 includes a disc portion 103a fixed to the base 102
and a hollowed shaft 103b extending from the disc portion 103a. A rotary
proximal portion 106 is rotatably supported to a periphery of the
hollowed shaft 103b via a pair of conical roller bearings 104, 104. Each
of the bearings 104, 105 is given a preload from a nut 110 screwed to an
end portion of the hollowed shaft 103b, thereby eliminating internal
backlashes.

[0039]The rotary proximal portion 106 includes a hollowed cylindrical
portion 106a supported by the bearings 104, 105, and a flange portion
106b extending outward in a radial direction from the hollowed
cylindrical portion 106a. A rotor bracket 107 is fixed to an internal
face (on the side of the base 102). The rotor bracket 107 taking an
L-shape in section is constructed of a flange portion 107a fitted to the
flange portion 106b and extending outward in the radial direction, and a
cylindrical rotor retaining portion 107b extending from an outer
peripheral edge of the flange portion 107a toward the inside (on the side
of the base 102) in the direction of the axial line. Rotors 114 each
consisting of permanent magnet are attached in alignment in the
peripheral direction to an internal peripheral face of the rotor
retaining portion 107b.

[0040]On the other hand, an annular torque meter 108 is secured to an
external side of the flange portion 106b in the form of being co-fastened
together with the rotor bracket 107 and the bolt being used in common.
Rollers 109 are secured via a multiplicity of bolts to an outer periphery
of the torque meter 108. The torque meter 108 detects the torque received
by the rollers 109 by way of strain etc and is well known, and hence its
in-depth description is omitted.

[0041]As illustrated in FIGS. 4 and 5, the roller 109 is configured by
sticking two sheets of plate members, and includes a flange portion 109a
fixed to the torque meter 108 and extending outward in the radial
direction but inward in the direction of the axial line, a cylindrical
outer peripheral portion 109b extending on both sides in the direction of
the axial line from the outer peripheral edge of the flange portion 109a,
and eight pieces of ribs 109c extending from an inner edge to the outer
edge of the flange portion 109a and disposed at equal intervals in the
peripheral direction. Note that the rollers 109 may be composed of
aluminum and fiber-reinforced plastic, and may also be constructed as one
integrated body without being limited to separate bodies.

[0042]FIG. 7 is a front view of the torque meter 108. FIG. 8 is a view of
the configuration cut off by a VIII-VIII line and viewed in the arrowhead
direction in FIG. 7. Referring to FIGS. 7 and 8, the torque meter 108
includes a proximal portion 108a fixed to the rotary proximal portion 106
and to the rotor bracket 107 by six pieces of large bolts LB (FIG. 6)
inserted through bolt holes 108b, and a collar portion 108c fixed to the
flange portion 109a of the roller 109 by a small bolt SB (FIG. 6)
inserted through a holt hole 108d. In the proximal portion 108a, a strain
gage SG is pasted onto a block-shaped measuring target portion 108e
formed between the neighboring holts 108b. Each strain gage SG is
connected to an unillustrated measuring circuit.

[0043]An outward portion, in the radial direction, of each measuring
target portion 108e is connected to the collar portion 108c via a
thin-plate-like connection portion 108f extending bidirectionally in
tangential direction therefrom. Note that a slit-shaped aperture 108g is
so formed as to extend toward the side face of the measuring target
portion 108e from the outside, in the radial direction, of the bolt hole
108b, and a slit-shaped aperture 108h is formed outward in the radial
direction of the measuring target portion 108e independently thereof,
thereby enabling the measuring target portion 108e to deform to some
extent when receiving the torque.

[0044]FIG. 9 is a view showing a force acting on between the roller 109
and the wheel T when measured. Referring to FIG. 9, with respect to a
contact point between the roller 109 and the wheel T, when a traveling
direction of the vehicle is set as the X-axis, a widthwise direction of
the vehicle is set as the Y-axis and a tangential direction of the roller
109 is set as the Z-axis, it follows that the roller 109 receives a force
(outer periphery tangential force) FX acting in the X-axis from the
wheel T, a force FY in the Y-axis direction, a force FZ in the
Z-axis direction, a moment θX about the X-axis, a moment
θX about the X-axis, a moment θY about the Y-axis
and a moment θZ about the Z-axis. This is termed "six force
components", and an apparatus capable of measuring all of the six force
components is called a six-force-component meter. The torque meter 108
can measure the six force components including dispersion forces other
than force in the traveling direction (the X-axis direction) of the
vehicle V that are applied to the roller 109, and therefore dynamically
analyzes the vehicle V with high accuracy.

[0045]Referring to FIG. 6, a support member 111 serving also as a cover is
secured with a bolt to an end face of the rotary proximal portion 106
inward in the radial direction of the torque meter 108. A right end, as
viewed in FIG. 6, of a connection shaft 112 extending through the
hollowed shaft 103b of the fixed shaft 103 engages with the support
member 111 in a way that rotates integrally. The other end of the
connection shaft 112 is connected to a resolver 113 disposed within a
recessed portion 103c formed at a root of the hollowed shaft 103b. The
resolver 113 magnetically detects a relative displacement between a
stator fitted to the fixed shaft 103 and a rotor fitted to the connection
shaft 112 and can detect relative rotations between the fixed shaft 103
and the connection shaft 112 on the basis of the relative replacement,
i.e., a rotating speed of the roller 109. The resolver 113 is, for
example, put on the market as a trade name [Singlsyn] by Tamagawa Seiki
Co., Ltd. As described above, a scheme of providing the resolver 113 on
the root side of the fixed shaft 103 intends to avoid magnetic
interference with the torque meter 108, however, if a proper shield is
employed, the resolver 113 can be provided in the vicinity of the torque
meter 108. Note that a means for detecting the rotating speed of the
roller 109 can involve using, without being limited to the resolver, a
variety of rotation detectors such as magnetic or optical encoders.

[0046]Referring to FIG. 6, a stator bracket 115 is fixed with a bolt to
the disc portion 103a of the fixed shaft 103. The stator bracket 115
taking an L shape in section is constructed of a flange portion 115a
fitted to the disc portion 103a and extending outward in the radial
direction, and of a cylindrical stator retaining portion 115b directed
outward in the direction of the axial line from the outer peripheral edge
of the flange portion 115a and extending inward in the radial direction
of the rotor retaining portion 107b. A stator 116 is fitted, with a
slight gap from the rotor 114, to the outer peripheral face of the stator
retaining portion 115b. The motor is structured by the rotor 114 and the
stator 116.

[0047]An unillustrated wiring extends along the surface of the stator
bracket 115 from a coil of the stator 116 and connects to an external
inverter unit (unillustrated). The coil of the stator 116 emits heat when
driving, and it is therefore preferable to form a plurality of fins 115c
at equal intervals ranging from the flange portion 115a to the stator
retaining portion 115b in order to enhance a heat radiation effect. These
fins 115c contribute, as reinforcing ribs, to improve rigidity of the
stator bracket 115.

[0048]Additionally, in the present embodiment, the stator retaining
portion 115b takes a double-cylindrical shape. More specifically, a
closed space is provided between an external wall 115d and an internal
wall 115e, and a jacket through which cooling water passes is formed in
this closed space. To be more specific, three partition walls 115f, 115g,
115h spaced away from each other in the direction of the axial line are
provided consecutively in the peripheral direction between the external
wall 115d and the internal wall 115e. When the cooling water is supplied
from outside via an inlet (unillustrated) of the partition wall 115f, the
cooling water flows clockwise (as viewed in the direction in FIG. 5)
within a path between the partition walls 115f and 115g, then, after
making a U-turn in any one of positions, flows counterclockwise (as
viewed in the direction in FIG. 5) within a path between the partition
walls 115g and 115h, and is discharged to outside from an unillustrated
outlet. This stator bracket 115 may be formed by casting and may also be
formed by joining cylindrical members having different diameters to each
other by welding.

[0049]An operation in the present embodiment will hereinafter be
described. As illustrated in FIG. 3, when turning ON an unillustrated
switch in the state where the drive wheels T, T of the vehicle V are
placed on the rollers 109, a high-frequency current is transmitted via
the wiring to the stator 116 from the inverter unit, the magnetic force
is thereby generated between the stator 116 and the rotor 114, whereby
the roller 109 can be rotationally driven by use of the magnetic force
via the rotary proximal portion 106. At this time, a minute rotational
deviation occurs corresponding to the torque between the proximal portion
108a and the collar portion 108b of the torque meter 108, consequently
the measuring target portion 108e gets elastically deformed, the strain
occurs in the strain gage SG, and hence a torque value can be detected
from a variation in resistance value. Accordingly, the resistance caused
when applying an engine brake of the vehicle can be measured with the
high accuracy by the torque meter 108.

[0050]Namely, according to the chassis dynamometer 100 in the present
embodiment, each of the flange portions 109a of the rollers 109 on which
the wheels of the vehicle are placed is connected via the torque meter
108 to the rotor bracket 107 of the rotor 114 of the motor, thereby
enabling the measurement of the torque to be avoided from being affected
by the bearings. Accordingly, an error in the measurement of the torque
is caused mainly by a windage loss of the roller 109. The windage loss,
which is determined based on the structure of the roller 109 and can be
reduced to the greatest possible degree, takes a stable value without
being influenced by a temperature after the structure has been determined
and can be precisely corrected by use of an experimental value. Further,
the rotary proximal portion 106 can be designed to have the extremely
high rigidity in terms of the mechanical structure because of using none
of a shaft torque meter, thereby enabling an evaluation of the torque
measurement to be realized in a fast response.

[0051]On the other hand, when the drive wheels T, T are rotated by the
power given from the engine, whereby the rollers 109 are rotationally
driven. At this time, the rotor 114 rotates via the rotary proximal
portion 106, and consequently the electric power is generated on the side
of the stator 116. Namely, it follows that the driving force supplied
from the drive wheels T, T can be converted into the electricity and
absorbed by using the motor as a generator. The driving force at this
time can be measured by the torque meter. Especially in the present
embodiment, the driving force generated at each of the drive wheels T, T
can be measured, and it is therefore feasible to confirm distribution of
the power distributed to the respective drive wheels by use of, e.g., a
differential mechanism. Further, in a so-called all-wheel-drive vehicle
such as a 4WD (four wheel drive) car, the chassis dynamometer 100 is
disposed at each wheel, thereby enabling the driving force to be measured
independently.

[0052]In the chassis dynamometer 100, even when the heat is evolved in the
coil of the stator 116, the stator retaining portion 115b of the stator
bracket 115 is cooled by the cooling water, and the respective portions
can be avoided from being affected by the heat.

[0053]Moreover, according to the chassis dynamometers 100 in the present
embodiment, the motors are disposed inward in the radial directions of
the rollers 109, 109 on which the drive wheels T, T of the vehicle V are
placed, thereby enabling the torsion rigidity of the rotation system to
be increased owing to the box-shaped high rigidity structure constructed
of the torque meter 108 and the rotary proximal portion 106 and the
rotational balance to be improved by concentrating heavy masses in a way
that saves the space. Further, since the vehicle load can be applied from
outward in the radial direction to the conical bearings 104, 105 that
bear the rollers 109, the flexural moment does not act unlike the case of
supporting the rotary shaft as by the conventional technology, and a long
life-span of the conical bearing can be ensured. Further, the motor is
provided inwardly of the roller 109, and hence the distance between the
rollers 109, 109 can be arbitrarily set. Accordingly, the chassis
dynamometers 100, 100 can be installed in adjustment to the positions of
the individual drive wheels T, T of the vehicle V, whereby a width of the
roller 109 can be reduced, an inertial mass can be restrained small, and
consequently a test for a low μ path can be reenacted on the bench
while saving the space.

[0054]FIG. 10 is a sectional view taken in the direction of the axial
line, showing a chassis dynamometer 100' according to another embodiment,
and FIG. 11 is a view of the configuration in FIG. 10 as viewed in an
arrowhead direction XI. FIG. 12 is an enlarged view of a portion depicted
along an arrowhead line XII in the configuration in FIG. 10.

[0055]In the present embodiment, the stator retaining portion 115b of the
stator bracket 115 is located outward in the radial direction of the
rotor retaining portion 107b of the rotor bracket 107, i.e., the rotor
114 is disposed inward in the radial direction of the stator 116, whereby
the diameter thereof can be restrained small and the inertial mass is
reduced. Other components are common to the embodiment discussed above
and marked with the same symbols and numerals, of which the descriptions
are omitted.

[0056]The present invention has been discussed so far in detail by way of
the embodiments but should not be construed in the way of being limited
to the embodiments discussed above, and can be, as a matter of course,
adequately modified and ameliorated within the range that does not
deviate from the gist of the invention. For example, part of the motor
may be extruded from the end portion of the rotor in the direction of the
axial line thereof.